## Issue being fixed or feature implemented
## What was done?
Feature requested by @QuantumExplorer and @iammadab.
This PR introduces `protx listdiff`: a more rich alternative of `protx
diff` RPC.
Currently, `protx diff` is returning data only required from SPV for SML
Coinbase MerkleMNListRoot calculation.
Platform team needed a similar RPC returning all the MNs data in order
to calculate the identities.
## How Has This Been Tested?
## Breaking Changes
## Checklist:
_Go over all the following points, and put an `x` in all the boxes that
apply._
- [x] I have performed a self-review of my own code
- [ ] I have commented my code, particularly in hard-to-understand areas
- [ ] I have added or updated relevant unit/integration/functional/e2e
tests
- [x] I have made corresponding changes to the documentation
- [x] I have assigned this pull request to a milestone _(for repository
code-owners and collaborators only)_
